T cell regulated hematopoiesis--molecular interactions in hematopoietic control by CD2 and interleukin 2

Studies are reviewed, which establish a novel regulatory role for the T cell surface molecule CD2 and the T cell lymphokine IL-2: Immunoregulation of hematopoiesis. IL-2 induces a receptor-specific inhibition of early erythroid progenitors. IL-2-induced inhibition of erythropoiesis is mediated by interferon-gamma protein release and is associated with interferon-gamma mRNA accumulation. CD3-triggered p55 IL-2 receptor expression is a prerequisite for IL-2-induced erythropoietic inhibition and is associated with p55 mRNA synthesis. Hematopoietic effects of IL-2 are mediated by CD2/LFA-3 receptor ligand interactions. The studies demonstrate that the regulatory roles of IL-2 and CD2 extend beyond governance of the immune system itself and can subserve to control red cell production in vitro.